A highly influential paper by Professor Chaitra Gopalappa of the Mechanical and Industrial Engineering Department was recently cited by the Centers for Disease Control and Prevention in its Morbidity and Mortality Weekly Report, Volume 66, November 28, 2017, as well as other publications. Gopalappa’s expertise is in advancing mathematical methodologies to derive information that might help in decision-making for public health strategies.

Gopalappa works closely with the Centers for Disease Control and Prevention and the World Health Organization on non-communicable diseases such as cancers and communicable diseases such as HIV. She does research that integrates methods from simulation modeling, stochastic processes, and optimization modeling for economic analysis of public health strategic plans. Gopalappa is also an expert at answering critical questions raised by the U.S. National HIV/AIDS Strategy (NHAS), developed in 2010.

Gopalappa’s cited paper was published in the journal Medical Decision Making and was entitled “Progression and transmission of HIV/AIDS (PATH 2.0).”Read abstract and paper »[2]

As Gopalappa explained in her cited paper, “HIV transmission is the result of complex dynamics in the risk behaviors, partnership choices, disease stage, and position along the HIV care continuum—individual characteristics that themselves can change over time. Capturing these dynamics and simulating transmissions to understand the chief sources of transmission remain important for prevention.”

In describing her methodology, Gopalappa said that the progression and transmission of HIV/AIDS is an agent-based model of a sample of 10,000 “people living with HIV” (PLWH), who represent all “men who have sex with men” (MSM) and heterosexuals living with HIV in the U.S.A. Persons uninfected were modeled as populations, stratified by risk and gender. The model integrated detailed individual-level data from several large national surveillance databases to dynamically simulate transmissions. The outcomes focused on estimation of average annual transmission rates from 2008 through 2011 by disease stage, HIV care continuum, and sexual risk group.

Gopalappa’s results indicated that “The relative risk of transmission of those in the acute phase was nine-times…that of those in the non-acute phase, although, on average, those with acute infections comprised 1% of all PLWH. Among those in the non-acute phase of infection, the relative risk of transmission was 24- to 50-times as high for those not on antiretroviral therapy (ART) treatment as compared with those on ART and who had achieved viral load suppression. The relative risk of transmission among MSM was 3.2-times…that of heterosexuals. Men who have sex with men and women generated 46% of sexually acquired transmissions among heterosexuals.”

Gopalappa’s paper concluded that her model results support a continued focus on early diagnosis, treatment, and adherence to ART treatment, with an emphasis on prevention efforts for MSM, a subgroup of whom appear to play a role in transmission to heterosexuals.

The number of persons newly infected with HIV in the U.S. was about 50,000 each year up until 2009. To address this critical problem, the first NHAS was developed in 2010, with a goal to reduce incidence by 25 percent by 2015; but, since that goal was never met, it was delayed until 2020. Gopalappa is currently receiving a grant of $1,567,348 from the National Institutes of Health (NIH) to answer several critical questions posed by the NHAS and to develop a new model and methods necessary for analyses of these crucial problems.
One fundamental impact of Gopalappa’s NIH research will be to help guide intervention decisions to best reach the goals of the NHAS, which is a national plan that serves as a “roadmap” for implementing interventions to reduce the incidence of HIV infections. (December 2017)